In recent years, our understanding of the psychology of visual perception has grown in parallel with our knowledge of the organization of extrastriate visual cortex. The relationship between the two fields, however, is still very much a mystery. The aim of the proposed research is to investigate the functions of extrastriate visual areas in motion and form perception through a combined application of neurophysiological, psychophysical and computational techniques. The first objective is to explore our ability to perceive motion of objects defined by nonluminant contrast cues, such as texture or depth. Psychophysical and physiological experiments have been designed to identify and characterize the neural systems mediating these perceptual abilities. The results should provide clues to the level of image representation used by cortical motion detectors. A second, related, objective is to examine the neural bases of perceptual phenomena attributed to a "long-range" motion system, especially the effects of stimulus form and contextual factors on motion perception. A third objective is to continue computational and physiological efforts to identify the neural mechanisms underlying perception of motion of two-dimensional patterns. This project will focus initially on the role of extrastriate area MT in motion perception, since much previous research has implicated this area in visual motion processing. Areas V1 and V2 will also be studied to determine how form encoding by neurons in these areas contributes to subsequent motion analysis by MT neurons. The long-term goal of this research is to obtain information that will aid in the treatment of neurologic disorders of vision caused by trauma, disease and developmental defects. The aims are pertinent to a variety of clinical applications including development of prostheses for the visually handicapped and treatment programs for perceptual deficits, as well as non-clinical applications such as design of machine-based vision systems for automated object recognition and methods for improving human performance during execution of complex visuomotor tasks.